1. Field of the Invention
This invention relates to a weapon guidance system and more particularly to a weapon guidance system employing beam transmission to provide guidance data.
2. Description of Related Information
Weapons guidance systems are a rather recent development. Early in warfare, weapons such as artillery and aerial bombs were initially aimed towards a target and received no further guidance after deployment. More modern weapons systems, such as guided missiles and guided bombs, use information received before initial deployment, as direction toward a target, and additional information received during weapon flight to improve the weapon's terminal accuracy.
One such system used in guided bombs and guided missiles is the "beam rider" wherein a laser beam is projected onto a target and a bomb or missile is launched in a trajectory to travel down the beam to the target. After the weapon is launched, any deviation of the weapon from the beam is corrected as required to reposition the weapon on the beam. Generally, these course corrections are of a greater magnitude than actually necessary to correct the trajectory of the weapon relative to the target since the beam is located much closer to the weapon than the target. The requirement to correct trajectory to the beam results in more stringent demands on the weapon guidance system than necessary to guide the weapon to the target.
The "beam rider" weapon guidance systems have several disadvantages in addition to requiring the guidance system to provide a greater magnitude of course correction than required to correct the weapon trajectory to the target. Another disadvantage is the requirement of maintaining the beam on the target during weapon delivery, which may be difficult because of the hostile environment of the target area. Furthermore, atmospheric conditions may not be conducive to beam transmissions over long distances, resulting in the weapon losing the beam reference before flight termination at the target. Still further, the target may detect the presence of the beam and take evasive action.
It is an object of the present invention to provide a guidance system to direct a weapon to a target in a manner adaptive to the actual trajectory of the weapon in flight relative to the target.
It is further an object of the present invention to provide a weapon guidance system that does not require continuous active target designation but which is passive relative to the target.
It is a still further object of the present invention to provide a guidance apparatus which periodically transmits signals to the weapon by which the weapon internal guidance system may determine its actual trajectory position relative to the target.